1. Technical Field
The present invention relates to a drive torque distribution apparatus which adjusts a torque distribution between a first drive shaft and a second drive shaft.
2. Related Art
International Publication No. 2011/76542 discloses a technique related to a drive torque distribution apparatus of this type. The drive torque distribution apparatus of International Publication No. 2011/76542 comprises a differential device, first, second, and third planetary gear mechanisms, and a motor. The motor has a stator and a rotor, and the rotor is linked to a sun gear of the first planetary gear mechanism. Carriers of the first and second planetary gear mechanisms are linked, and rotation of the sun gear of the second planetary gear mechanism is fixed. A ring gear of the first planetary gear mechanism is linked to a ring gear of the third planetary gear mechanism, a ring gear of the second planetary gear mechanism is linked to a sun gear of the third planetary gear mechanism, and a pinion gear (planetary gear) of the third planetary gear mechanism is linked to a pinion gear of the differential device.
In International Publication No. 2011/76542, when a right side gear and a left side gear of the differential device (a right drive shaft and a left drive shaft) rotate in the same direction at equal rotational speeds, the rotational speed of the ring gear of the first planetary gear mechanism and the rotational speed of the ring gear of the second planetary gear mechanism are equal to each other, and the rotation of the rotor is stopped. On the other hand, when a torque is applied from the stator to the rotor to rotationally drive the rotor, a rotational difference is caused between the ring gear and the sun gear of the third planetary gear mechanism (the ring gear of the first planetary gear mechanism and the ring gear of the second planetary gear mechanism), and the pinion gear of the third planetary gear mechanism integrally rotates (spins) with the pinion gear of the differential device. Due to the spinning of the pinion gear of the differential device, a rotational difference is caused between the right side gear and the left side gear (the right drive shaft and the left drive shaft), and a torque distribution between the right drive shaft and the left drive shaft is changed according to the torque applied from the stator to the rotor.
In International Publication No. 2011/76542, a torque is applied from the stator to the rotor to rotationally drive the rotor, so that the pinion gear of the differential device rotates (spins), and the torque distribution between the right drive shaft and the left drive shaft is changed. However, in order to realize the spinning of the pinion gear of the differential device by the rotational driving of the rotor, it is necessary to use three planetary gear mechanisms, resulting in complexity of the structure for adjusting the torque distribution. In addition, when the right side gear and the left side gear (the right drive shaft and the left drive shaft) of the differential device rotate in the same direction with equal rotational speeds, the rotation of the rotor is stopped. However, in this case, the sun gear, pinion gear, and ring gear of the first and second planetary gear mechanisms are not integrally rotated, and a loss is caused due to occurrence of a rotational difference (differential) between the sun gear and the ring gear due to the spinning of the pinion gear. An advantage of the present invention is that a torque distribution between first and second drive shafts is adjusted while not complicating the structure, and the loss when the first drive shaft and the second drive shaft rotate at equal rotational speeds is reduced.